At first, dreadlocks should be washed sparingly. Experts differ somewhat about how often to wash, but about once a week initially is the general consensus. Consider covering your entire head with a nylon stocking at this stage, and letting the soap run through to prevent damage to the fragile locks.
If you have kinky hair, the texture of your hair works to your advantage at this stage. If locks start to come undone, they can be retwisted according to the twisting method you used to start them. Every few days, you can use a technique called palm rolling to encourage the hair to grow into the spiral pattern of dreadlocks. Using your flattened palms, take each lock and roll it in a clockwise direction.
Over the first few months, the curls and twists will begin to form knots close to the roots. This is sometimes called the budding stage, and is the first step to your hair forming secure locks. How long this takes will vary depending on your hair texture and level of maintenance. Hair may begin to form dreadlocks as early as two months, but sometimes not until after six months to a year.
At this point, your dreadlocks will be in the locking stage. You'll still want to palm roll your dreads to encourage the right kind of growth, but not as often, and you won't have to worry about the dreads coming out. At the root, the hair growing into the dreads will look loose for a few inches, but that looseness is necessary for new hair to grow in the right pattern.
For straight hair, the same stages don't necessarily apply, because you've artificially created the knots that form during the budding stage. Instead, it's important to simply keep the new dreads in the proper shape by reapplying a layer of wax a few times a week (if you're using wax). Palm roll the dreadlocks regularly to encourage hair to grow in the right pattern from the root and maintain a cylindrical shape.
For all types of hair, the eventual goal is a more mature stage, which occurs after two years or more. At this point, the pattern of hair growth is more or less permanent, and hair that has fallen out of your scalp remains inside the dread, adding length beyond what your individual hair could reach.